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Hi,
PLEASE HELP ON HOW TO OPTIMALLY WIRE MY NEW ADDED XL16I 4ton COOLING AC COMPRESSOR TO THE XC95m FURNACE (5ton) AND TO MY TCONT900A THERMOSTAT, SUCH AS THE 2 STAGES ON XL16I WILL BOTH WORK FINE. I HAVE NOW THE FEELING THE AC UNIT WORKS ALL TIME FULL SPEED, BLOWER WORKS STRONG LIKE WHEN HEATING IN HARDEST WINTER, PROBABLY SECOND STAGE KICKS IN. BLOWER NEVER CHANGES FLOW STREAM NO MATTER HOW LONG IT WORKS AND THE TEMP DIFF TO ACHIEVE. THEN STOPS WHEN REACHES TARGET, WILL THEN START WITH SAME HIGH INTENSITY. I WAS EXPECTING ALL TO BE SMOOTHER, KICK FIRST STAGE WITH LOWER BLOWER POWER AND THEN IF NEEDED AFTER A WHILE KICKS IN 2ND STAGE, STRONG. NOW THE CONNECTIONS ARE: 1) TCONT900A TO FURNACE: D TO D, BLUE TO B, RED TO R 2) FURNACE TO XL16I: Y1 TO YELLOW, Y2 TO BROWN, B TO BLUE. THERMOSTAT IS SET FOR COOLING NBR OF STAGES = 2 AND COOLING 1-ST STAGE = 75%. BUT I NEVER SEEN A DIFFERENCE BETWEEN THE 2 STAGES, I DON'T THINK I GET THE MOST FROM THE INVESTMENT. I COULD NOT FIND A CLEAR WIRING DIAGRAM, MANUAL FOR CONNFORTLINK II (TCONT900A) ONLY SPECIFIES CONNECTION TO INTERNAL COMMUNICATING FURNACE (OK UP TO HERE) AND A SINGLE-STAGE (!!) NON_COMMUNICATING COOLING DEVICE. SINCE I DIDN'T KNOW ENOUGH AS TO PROBABLY BUY THE XL20i, NEED TO MAKE THIS WORK FINE. THANK YOU!

You'd think that after what, 10 years, Trane might do something to solve the XL16i "issues" with pairing it with their furnaces and communicating equipment. I remember wiring up a couple relays to make dehumidify on demand at least sort-of work. I forced the unit into 2nd stage but left it on low airflow when humidty was high. It helped, but ultimately it was oversized and used almsot the same amount of power as the mismatched but properly sized 15 y/o 8 SEER unit it replaced.

Probably jsut as well off using a Honeywell Visionpro IAQ or Prestige thermostat.

If the blower speed is 75% you probably won't tell a difference in blower speed from 1st to 2nd stage, and you really can't tell a difference in sound on the outside unit.

While I've sold several of the 16i heat pumps not A/Cs, I have never been sold on the 2 step scroll technology. I don't see where the drop in capacity is enough to warrant the cost. I have sold a lot of the 19 & 20i units with the 50% low speed 100% high speed as now you have a noticeable change in operation, one you can hear and feel.

Thank you all for answering so promptly! I will try to organize my acknowledgment on this. (1) Based on component modules, described wiring and observed symptom, do we know exactly what the existing system cannot accomplish? Is it that it runs only in 2-nd stage, only in 1-st stage or else? (2) I understand remedy exists in the form of: (2.a) a relay pack that makes xl16i work well in a communicating system (mark beiser, chuckcrj, motoguy128), I will request it from installer (2.b) use a better fit (downgrade to non-communicating?) thermostat of type Honeywell Visionpro IAQ or Prestige thermostat (motoguy128) (3) please advise if going for a full communicating system and replacing xl16i with a xl20i (only one avail from Trane I think) could be considered instead patching (many good hundred $ more probably). But then I understand I will have a clearly 50/100 (2 scroll compressors?) working 15-20 mins in 1-st stage 1 (way lower air flow that I have now) and only jumping to 2-nd stage if can't keep pace with warmth. Also please indicate if such fully communicating system will permit to adjust the pace (strokes / min or power) of AC to other than 50/100 (somewhat degrading seer). Or even considering a smaller unit like 3.5 ton XL20i. Uh, really abusing your time but ignorance is unbearable. Trane does not have a Cust Support line to answer these questions and manuals I got are just brief specs.